The present invention relates generally to semiconductor integrated circuit manufacturing processes. More specifically, the present invention relates to applying encapsulant material onto the surfaces of semiconductor wafers.
As is well known in the art, integrated circuit devices are fabricated on semiconductor wafers. After the integrated circuit devices (or die) have been fabricated, they are separated from the wafer during what is referred to as a singulation process. One such singulation process, referred to as a saw operation, utilizes a saw having a circular (or other appropriate shape) blade to cut through the wafers along what are referred to as scribe lines (that delineate the individual die). One problem associated with this saw operation, however, is that when the saw blade cuts through the wafer, the surfaces of the wafer can be damaged due to stresses induced in the wafer that typically results in chipping, cracking, etc.
A conventional approach to protecting the surfaces of the wafer during the saw operation utilizes a protective layer of encapsulant material (such as epoxy). In addition to protecting the wafer surfaces, the protective layer of encapsulant provides a surface upon which identifying indicia (i.e., markings) can be placed. These markings are typically used to identify particular classes, or grades, of die (based upon, for example, speed, power, etc.). In order, therefore, to provide optimal protection as well as a surface suitable for clear marking, the protective layer of encapsulating material must be as uniform as possible since a non-uniform layer of encapsulant substantially reduces the protective properties of the encapsulant layer as well as reduces the ability to produce a clear and legible mark.
One approach to forming a uniform layer of encapsulant involves the use of encapsulant applicators that typically take the form of what is referred to as squeegees. A conventionally structured squeegee, however, has the unfortunate tendency to deflect under pressure during a smoothing operation resulting in a non-uniform layer of encapsulant.
In view of the foregoing, an apparatus and a method of forming a layer of encapsulant material having a uniform thickness onto semiconductor wafers would be desirable
The present invention provides an encapsulant applicator and a method for using the applicator capable of forming a substantially uniform layer of encapsulant material on a surface of a semiconductor wafer. The applicator includes a flexor formed of a resilient material having a first end, and a substantially rigid blade. The blade has a first edge and a second edge, wherein the first edge is attached to the first end of the flexor in a way that during a smoothing process, a force applied through the flexor is distributed across the second edge of the blade.
Another aspect of the invention pertains to a system for forming a substantially uniform layer of material on a surface of a semiconductor wafer. The system of the present invention includes a stencil, an applicator and a conveyor device. The stencil is placed over the surface of the wafer so that an opening in the stencil exposes a portion of the surface of the wafer. The applicator includes a flexor formed of a resilient material having a first end and a second end and a substantially rigid blade having a first edge and a second edge. The first edge of the blade is attached to the first end of the flexor in a way that during a smoothing process, a force applied through the flexor is distributed across the second edge of the blade. The conveyor device is connected to the second end of the flexor so that during the smoothing process, the conveyor device moves the applicator across the opening of the stencil.
Yet another aspect of the invention pertains to a method for applying a substantially uniform layer of flowable material to a surface of a semiconductor wafer using the applicator as described. The method involves sweeping the applicator across an opening of a stencil such that the applicator is in contact with the stencil.